In modern dairy farm industry there are continuous research and development activities in order to improve the efficiency of various activities such as machine milking, which, inter alia, involves increased milk yield and reduced milking time, while, naturally, ethical aspects as well as animal care are considered.
Machine milking, as known in the art, generally utilizes teat cups and vacuum sources to perform the milking function. In such systems each teat is contained within a teat cup having a teat receiving liner, inside the teat cup next to the teat. A working vacuum is applied to the interior of each teat cup liner to draw the milk from the teat, with the teat liners periodically opened and collapsed by applications of a pulsating massage vacuum between the liner and the inside of the cup. This periodic working of the teat liners results in the periodic flow of milk from each teat into a receiving vessel, and constitutes the actual milking of the cow.
Milking preparation involves the first phases of milking in which the teat is stimulated in order to stimulate the milk ejection reflex and induce milk letdown.
GB 1 248 648 discloses a milking machine with a flow rate sensing device in a pipeline between the teat cup liners of the rear cups and a milk receiver held under partial vacuum such that the device operates a control means for varying the degree of vacuum between a working high vacuum and an idling low vacuum. Vacuum lines having different pressures (250 mms Hg and 550 mms Hg as given) are connected through hose pincher means to the milk receiver and through pulsators of differing frequency to the teat cups. When no milk flows through the device, the control valve, having one connection to vacuum and another to the atmosphere, causes pistons to operate the pincher means such that the milk receiver and teat cup liners are connected to the lower vacuum 550 mms Hg and the pulsator of lower frequency is connected to the teat cups, while during a flow of milk, impulses from the milk sensing device transmitted pneumatically to the control valve cause the pistons to move to change the positions of pincher means thereby connecting the higher vacuum to the milk receiver and the faster pulsator to the teat cups.